The use of a cable TV system as an alternative local loop instead of telco (telephone company) copper wires has been proposed many times over the years. A few systems have been built which use separate frequency division multiplexed carriers for each telephone, but the economics has not been competitive, nor the performance fully acceptable. Some systems have been proposed which use fiber optic lines carrying analog cable TV signals together with PCN (Personal Communications Network) digital voice telephone signals to distribution pedestals serving a cluster of houses with both TV and telephones. Today, such alternative technologies remain higher cost alternatives than the present use of separate telephone plants, and separate cable TV systems (Ref: Johnson, Leland L. and David P. Reed, RESIDENTIAL BROADBAND SERVICES BY TELEPHONE COMPANIES?, The RAND Corp., June 1990).
Fiber optic cable is increasingly being used in new and rebuilt cable TV systems to replace the large diameter coaxial trunk cables carrying programs from cable TV head-ends to the feeder cable network. TV signals are transmitted using AM (and sometimes FM) modulation on fiber optic cables. These signals are converted to electrical signals at the feeder cable junction. This produces higher quality TV performance at a price comparable to an all coaxial cable TV system (Ref. Chiddex, James, "FIBER OPTIC IMPLEMENTATION: A CASE STUDY", Communications Engineering and Design September 1989, p. 8).
PCN which uses small radio telephones have been developed in Europe, the Far East and in the U.S. In the U.S. a plethora of applicants are filing for PCN licenses from the FCC in the hope that a monopoly value will accrue to the paper license similar to the cellular radio license experience, where the paper licenses were issued by lottery with the intention of being resold at a high price to the eventual system builder.
The closest relevant prior art of the present invention found was in a recent proposal by the Jerrold division of General Instruments, Co. described in a public presentation at the Cable TV Laboratories, Denver, Colo. Cable TV Laboratories is sponsored by a consortium of cable TV operators). In the presentation, Jerrold proposes using TV cable to connect PCN type telephone instruments to the telephone central office. PCN is a low power cellular approach and offers a simpler and lower cost base station arrangement than conventional cellular radio. Initially PCN was used to refer to wireless telephone calls that could only initiate calls. But, this definition of PCN is evolving towards initiation and receiving inbound calls. The shorter range of PCN, generally up to 600 meters, allows lower power levels than required by longer range cellular radio. In turn, this lower power requirement allows the use of smaller hand held telephone instruments with a longer battery life between recharges than the larger, more powerful, cellular radio telephones.
In the Jerrold proposal, PCN signals within the vicinity of a house are received by an active coupling unit physically connected to the end of the TV drop cable. These signals are transmitted upstream ("Upstream" refers to the direction toward the cable TV head-end, and "downstream" refers to the direction toward the terminal devices) via the drop cable. The drop cable connects to the TV feeder cable. An active coupling unit, used within the house, contains an amplifier, an AGC control circuit, a microprocessor and a varilloser (an amplitude limiting device) to provide a signal levelling capability to prevent strong PCN signals from swamping out other signals on the cable. The arrangement described creates a transmission path for frequency division of PCN device signals over the cable TV system.
It would be desirable to have a system that overcomes the limitations of the known proposals and describes a combined cable TV plus telephone system technology which appears to offer greater capabilities and at a potentially lower cost than known alternatives. More specifically, it would be desirable to have a system that adds telephone and data capability to existing cable TV systems, with special applicability to cable TV systems using fiber-to-the-feeder configurations. It would further be desirable to have a total end-to-end solution, starting with cell relay packets generated within cordless telephone instruments and thence transmitted through the cable TV system to seamlessly interconnecting with SONET (synchronous optical network) fiber optic systems operating in the ATM (asychronous time multiplexing) mode for connection to fast packet switches. The present invention provides such a system.